The Hebrew word kippah literally means dome. Yarmulke and skullcap are other common terms for this head covering that is one of the most familiar symbols of Judaism.

As opposed to what some might be expecting to hear, wearing a kippah has nothing to do with the Torah or its commandments. The practice evolved from a single statement in the Babylonian Talmud, in which Rabbi Huna says he would not walk a distance of four cubits (six feet) with an uncovered head, “since the Divine Presence is above my head.” Over the years, keeping one’s head covered became a sign of humility before God.

Today, observant Jewish males (as well as a much smaller share of females) wear kippot at all times; many other Jews will don a skullcap only during Jewish rituals, when praying in synagogue or temple, or while eating.

However, as late as the mid-18th century, the Vilna Gaon - at the time, the undeniable leader of European Jewry - contended that one is never obligated to wear a head covering, even when reciting a blessing. If he said such a thing today, he would no doubt be accused of heresy, because in the current religious mindset, wearing a kippah is considered compulsory for a Jewish man or boy.

How did this the practice come to be so prevalent? As animosity between Jews and Christians in Europe increased over the centuries, wearing a kippah evolved into a symbol of non-Christianity for Jews. A Christian removes his hat as he walks into church, so Judaism sought to differentiate itself by requiring adherents to cover their heads when entering a synagogue.

It follows, then, that Sephardic Jews in North Africa and the Middle East – where Jewish-Christian hostility was not a factor – were not raised with the same strong sense of kippah as abiding sign of Jewish identity. It wasn’t until they relocated to Israel and joined the larger community of Jews here that religious Sephardic Jews adopted the practice on a widespread scale. Witness a fairly recent ruling by Rabbi Ovadia Yosef, the leading light of 20th century Sephardic Jewry, who ruled that a kippah should be worn at all times in order “to show affiliation with the religiously observant community.”

Kippah styles often vary according to subgroup in the religious world. Generally speaking, the larger the kippah, the more religiously observant the wearer. Ultra-Orthodox Jews wear a plain black velvet kippah, although some Chassidim opt for a little white model with a cute pom-pom. Religious Zionists wear a colorful knitted kippah with a design, but if the wearer’s politics are left of center, he might differentiate himself from the rest of the crowd with an all-black knitted kippah. More liberal Jews will often choose to wear a beautifully embroidered Bukharan or Uzbeki kippa. And then there are the folks who go to the Western Wall or attend temple services or find themselves at a Jewish funeral but haven’t equipped themselves in advance with a head covering: They are left to make do with the cheap acetate or cardboard handouts.

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